Hydrocarbon conversion processes using catalysts are often subject to catalyst regeneration and replacement requirements resulting from “poisoning” or “deactivation” of the catalyst by one or more impurities contained in the hydrocarbon feedstock. Short catalyst cycle length often results in both more frequent catalyst regeneration requirements and reduced ultimate life of the catalyst before replacement is necessary. Catalyst replacement often involves a process shutdown, lost production, and significant costs. In many cases, catalyst cycle length needs to be improved by preventing coke-forming and/or reducing “poisoning”. Various processes have been developed for removal of such impurities prior to contact with the catalyst.
Alkyl aromatic compounds such as cumene and ethylbenzene are often produced by reaction of aromatics and olefins in the presence of acidic molecular sieve catalysts. Liquid phase operation of aromatics alkylation processes has often been found to result in reduced operating costs as well as fewer undesirable byproducts than earlier vapor phase technologies.
Catalysts that can be used for alkylation of benzene with ethylene/propylene and also for transalkylation of benzene and polyethylbenzenes/polyisopropylbenzenes in liquid phase include zeolite beta, zeolite Y, zeolite omega, ZSM-5, ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68, Faujasite, Mordenite, porous crystalline magnesium silicates, and tungstate modified zirconia, all of which are known in the art.
Water as one of the impurities in the feed may impact the activity, selectivity, and the life of the molecular sieve catalyst. During the alkylation/transalkylation processes, the catalyst ages due to the deposition of coke and other deleterious materials on the catalyst. Such catalyst aging causes a decrease in the catalyst's activity for the conversion of reactants to products. To restore a catalyst's activity, the catalyst is often regenerated by controlled oxidation in air, or by other means. Following regeneration, the catalyst's activity is restored to a certain degree. However, the regenerated catalyst often has a reduced selectivity and activity to produce the desired monoalkylated compound, and increased amounts of the more undesirable polyalkylated impurities are produced. Therefore, there is a need for improved alkylation and/or transalkylation catalyst life. We surprisingly found that the catalyst life of an alkylation and/or translation catalyst may be improved by co-feeding water.